/* ----------------------------------------------------------------------
 * Project:      CMSIS DSP Library
 * Title:        arm_atan2_f32.c
 * Description:  float32 Arc tangent of y/x
 *
 * $Date:        22 April 2022
 * $Revision:    V1.10.0
 *
 * Target Processor: Cortex-M and Cortex-A cores
 * -------------------------------------------------------------------- */
/*
 * Copyright (C) 2010-2022 ARM Limited or its affiliates. All rights reserved.
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 (the License); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#include "arm_atan2_f32.h"

/*

atan for argument between in [0, 1.0]


*/

#define ATANHALFF32 0.463648f
#define PIHALFF32 1.5707963267948966192313f

#define ATAN2_NB_COEFS_F32 10

static const float atan2_coefs_f32[ATAN2_NB_COEFS_F32] = {0.0f, 1.0000001638308195518f, -0.0000228941363602264f, -0.3328086544578890873f, -0.004404814619311061f, 0.2162217461808173258f, -0.0207504842057097504f, -0.1745263362250363339f, 0.1340557235283553386f, -0.0323664125927477625f};

float arm_atan_limited_f32(float x)
{
  float res = atan2_coefs_f32[ATAN2_NB_COEFS_F32 - 1];
  int i = 1;
  for (i = 1; i < ATAN2_NB_COEFS_F32; i++)
  {
    res = x * res + atan2_coefs_f32[ATAN2_NB_COEFS_F32 - 1 - i];
  }

  return (res);
}

float arm_atan_f32(float x)
{
  int sign = 0;
  float res = 0.0f;

  if (x < 0.0f)
  {
    sign = 1;
    x = -x;
  }

  if (x > 1.0f)
  {
    x = 1.0f / x;
    res = PIHALFF32 - arm_atan_limited_f32(x);
  }
  else
  {
    res += arm_atan_limited_f32(x);
  }

  if (sign)
  {
    res = -res;
  }

  return (res);
}

/**
  @ingroup groupFastMath
 */

/**
  @defgroup atan2 ArcTan2

  Computing Arc tangent only using the ratio y/x is not enough to determine the angle
  since there is an indeterminacy. Opposite quadrants are giving the same ratio.

  ArcTan2 is not using y/x to compute the angle but y and x and use the sign of y and x
  to determine the quadrant.

 */

/**
  @addtogroup atan2
  @{
 */

/**
  @brief       Arc Tangent of y/x using sign of y and x to get right quadrant
  @param[in]   y  y coordinate
  @param[in]   x  x coordinate
  @param[out]  result  Result
  @return  error status.

  @par         Compute the Arc tangent of y/x:
                   The sign of y and x are used to determine the right quadrant
                   and compute the right angle.
*/

float arm_atan2_f32(float y, float x)
{
  if (x > 0.0f)
  {
    return arm_atan_f32(y / x);
  }
  if (x < 0.0f)
  {
    if (y > 0.0f)
    {
      return arm_atan_f32(y / x) + PI;
    }
    else
    {
      return arm_atan_f32(y / x) - PI;
    }
  }
  if (x == 0.0f)
  {
    if (y > 0.0f)
    {
      return PIHALFF32;
    }
    if (y < 0.0f)
    {
      return -PIHALFF32;
    }
  }
  return 0.0f;
}
